1. Field of the Invention
This invention relates to an electronic balance, and more particularly, to an electronic balance utilizing electromagnetism induced in response to a load applied thereto.
2. Description of the Prior Art
In general, known electronic balances are designed to weigh an object placed on the pan or tray by balancing the applied load and a force induced in the coil placed in a magnetic field and measuring the current value obtained therethrough. In this type of balances the Joule heat liberated in the coil varies in a relatively large range in accordance with the load, that is, the weight of an object placed on the balance. This causes temperature variations inside the balance, whereby its mechanical and electrical components are subjected to detrimental temperature changes. This is likely to cause an error in measuring the weight, and spoil the accuracy and reliability which are considered as essential to the balance.
To overcome this problem of temperature variations, there have been many proposal, among which is the employment of an extra heat generator near the coil. The heat generated by it is controlled to compensate for changes in the heat liberated by the coil, thus maintaining the thermal equilibrium. However, it is not advantageous to provide an additional heat generator because of the resulting structural complicacy and high cost.
The present invention aims at solving the problems pointed out above with respect to the known electronic balances, and has for its object to provide an improved electronic balance capable of controlling the heat liberated in the coil at a constant value irrespective of the amount of an applied load, or the application or nonapplication of a load.
Another object of the present invention is to provide an improved electronic balance capable of measuring a load applied thereto either in the positive direction or the negative direction.
Other objects and advantages of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific embodiments are given by way of illustration only, since various changes and modifications within the spirit of the invention will become apparent to those skilled in the art from this description.